The present invention relates to a spacer for roller bodies, which are guided in a roller bearing, in particular a linear guide, and which have an axis of symmetry about which they roll in a revolution path of the roller bearing. The invention furthermore relates to a linear device having such spacers.
In roller bearings, for noise abatement and to improve the rolling behavior of the roller bodies, the attempt is made to guide the roller bodies by means of suitable guide structures, such as cages, which are intended to prevent the roller bodies from entering into direct contact with one another, or to prevent overly great spacings from occurring between the roller bodies. In roller bodies that have an axis of symmetry which defines their rolling axis, it is furthermore important to avoid tilting of the axes of symmetry of the roller bodies relative to one another during their rolling motion.
The term linear devices should be understood to mean in particular linear guides and linear drives. It is characteristic for a linear guide or a linear drive that revolution path of the roller bodies alternates between rectilinear and curved portions, or between portions of variously pronounced curvature. This makes it especially problematic to guide roller bodies by suitable guide structures, since on the one hand a certain rigidity of the guide structure is required for good guidance, but on the other, because of the different path radii, sufficient flexibility of the guide structure is necessary, and therefore completely rigid cages, of the kind that are usual with roller bearings, cannot be considered.
In the prior art, various principles for guiding roller bodies in linear guides have been considered. On the one hand, it is known to discard the concept of a cage entirely and to separate the roller bodies from one another only by means of spacer bodies, preferably made from plastic, that are located loosely between the roller bodies. Such an arrangement is intrinsically incapable of preventing the spacings between the roller bodies from increasing in certain situations. If these spacings become too great, there is the danger that the spacer bodies will become jammed. Moreover, such different spacings of the roller bodies contribute to noise production. In the case of roller- or barrel-shaped roller bodies, there is the additional problem that as a result of forces acting on the roller bodies as they revolve, they rolling axes of the roller bodies, which are defined by the axis of symmetry of the roller bodies, relative to one another will tilt, which cannot be prevented by loose spacer bodies. The roller bodies themselves must therefore be guided by their face ends on the boundary walls of the revolution path.
From German Utility Model DE 20 2004 001 812 U1, it is for instance known to support rollers of a linear guide individually in a pocket. The pocket is formed by two separator elements, resting on the rolling faces of the rollers, that are connected on the sides by a curved tension belt that is guided past the face ends of the rollers.
To improve the guidance of the roller bodies, German Patent Disclosure DE 24 16 198, for roller-shaped roller bodies, proposes located two successive rollers together in an intrinsically rigid sheet-metal retaining element. This retaining element, on its face ends, has the cylindrical contours of the contact faces, which are adapted to the rolling faces of the rollers and are connected by two bracketlike guide parts. The sheet-metal guide parts are shaped such that they provide for the requisite rigidity of the retaining element and also prevent bending both in the direction of the rolling axis of the roller bodies and bending transversely to the rolling axis of the roller bodies. They are furthermore connected to one another by a rib that separates the two successive rollers from one another.
The guide parts rest with a short side on the face ends of the rollers inserted into the retaining element, and they engage a guide groove of the revolution path. The individual retaining elements follow one another loosely in the revolution path. Because of the rigid guidance of two rollers, for the same play of the guide parts in the guide groove, a smaller tilt angle of the rolling axes is attained than if the rollers are guided individually.
Alternatively, for better guidance of roller bodies in linear devices, it is proposed that the roller bodies be guided by flexible connecting elements on the order of a chain of roller bodies. The roller body chain is formed by a flexible connection belt, in which pockets are formed for receiving the individual roller bodies. For a better hold of the roller bodies in the pockets, as a rule retention shells, adapted to the contours of the rolling faces of the roller bodies, are formed on the face ends of the pockets. The flexibility of the connecting belt makes it possible for the belt to adapt its bend if the radius of curvature of the revolution path changes. For that purpose, it can additionally be guided in a guide groove (see for instance European Patent Disclosure EP 1 403 541 B1). A problem with roller body chains is in particular the adjustment of the most uniform possible bend of the connecting belt, above all for short deflection radii. The flexibility of the connection belt is therefore of decisive significance.
Finally, from US Patent Disclosure 2006/0120637 A1, it is known to shorten the length of a roller chain enough that only two pockets for rollers to be received are embodied in the flexible connection belt, so that even narrow deflection radii can be made possible. Because of the short length of the chain and the flexibility of the connection belt, however, in this embodiment a certain tilt of the roller axes to one another must be accepted into the bargain.
A further variant of a cage for a linear guide is shown in German Patent DE 42 11 400 C2. In this variant, the cage is made up individual members that are joined to one another in articulated fashion. From a middle rib part of each chain link, two tab parts extend orthogonally to each side. The roller bodies are supported in a pocket that is formed by slipping the tab parts, to be oriented toward one another, of two chain links onto one another and locking them at a pivot point. Although by means of this chain a fixation of the spacings of successive roller bodies is possible, nevertheless, because of the unavoidable play between two successive chain parts, guidance of the roller bodies in such a way as to avoid tilting of the rolling axis is not possible.